fix(pebble): avoid pydantic warning for exec checks

rockcraft/pebble.py

@@ -189,16 +189,25 @@ class ExecCheck(_BaseCheck):
     exec: ExecCheckOptions
 
 
-def _get_check_tag(check: Mapping[str, Any]) -> str:
+def _get_check_tag(check: Mapping[str, Any] | _BaseCheck) -> str:
+    if isinstance(check, HttpCheck):
+        return "http"
+    if isinstance(check, TcpCheck):
+        return "tcp"
+    if isinstance(check, ExecCheck):
+        return "exec"
+    if not isinstance(check, Mapping):
+        raise CraftValidationError(f"Unknown check type for {check!r}.")
+
     tags = ("http", "tcp", "exec")
-    check_types = check.keys() & tags
+    check_types = [tag for tag in tags if tag in check]
     match len(check_types):
         case 0:
             raise CraftValidationError(
                 f"Must specify exactly one of {', '.join(tags)} for each check."
             )
         case 1:
-            return check_types.pop()
+            return check_types[0]
         case _:
             raise CraftValidationError(
                 f"Multiple check types specified ({', '.join(sorted(check_types))}). "

tests/unit/test_project.py

@@ -17,8 +17,9 @@
 import datetime
 import os
 import subprocess
+import warnings
 from pathlib import Path
-from typing import cast
+from typing import Any, cast
 
 import pydantic
 import pytest
@@ -859,6 +860,37 @@ def test_provider_base(base, expected_base):
     assert actual_base == expected_base
 
 
+def test_project_marshal_exec_check_emits_no_pydantic_warning():
+    yaml_data = {
+        "name": "gubernator",
+        "version": "3.0.0",
+        "summary": "High-performance, distributed rate-limiting service",
+        "description": "example",
+        "base": "ubuntu@24.04",
+        "platforms": {"amd64": None},
+        "parts": {"foo": {"plugin": "nil"}},
+        "checks": {
+            "online": {
+                "override": "replace",
+                "period": "3s",
+                "exec": {"command": "/bin/healthcheck"},
+            }
+        },
+    }
+
+    project = Project.unmarshal(yaml_data)
+
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        dumped = project.marshal()
+
+    checks = cast(dict[str, Any], dumped["checks"])
+    assert checks["online"]["exec"]["command"] == "/bin/healthcheck"
+    assert not any(
+        "PydanticSerializationUnexpectedValue" in str(w.message) for w in caught
+    )
+
+
 def test_provider_base_error():
     with pytest.raises(ValueError, match="Unknown base 'unknown'"):
         Project._providers_base("unknown")  # pylint: disable=protected-access